Electric switch



Aug. 17 19371 ago. WiLMS ET A1.

ELECTRIC SWITCH 2 Sheets-Sheet 1 Original Filed July 11, 1955 Fig.1,

N m T Q L u S m G v 3 l Qwm [71/51271/ Z7. ifi/ms H5275 .F fz rsm Alilg.17, 1937. G O WILMS ET AL 2,090,179

. ELECTRIC SWITCH Original Filed July 11, 1935 2 Sheets-Sheet 2 Imum iin0 ill g wm f izxsfcn/ L7. Wz/zzzs i H5275 fpfprspn Patented Aug. 17,1937 UNITED STATES PATENT OFFICE.

Wauwatosa, Wls., assignors to Allen-Bradley Company, Milwaukee, Wis., acorporation of Wisconsin Original application July 11, 1935, Serial No.

30,790. Divided and 8, 1937, Serial No. 119,555

3 Claims.

This invention relates to improvements in electric switches and refersmore particularly to electromagnetically actuated control switches ofthe type shown in Reissue Patent No. 20,094, issued 5 to Gustav-O.Wilms, et al., September 1, 1936 and is a division of application SerialNo. 30,790, filed July 11, 1935, now Patent No. 2,071,149, February 16,1937.

As in the patent above noted, the switch of this invention is of thesolenoid type wherein the movable contacts have a straight line motionto and from engagement with their respective stationary contacts, but inthis instance all of the contacts are enclosed within a novel insulatedare enclosing chamber so constructed that while it completely enclosesthe contacts, access for inspection and replacement of contacts isreadily had. The movable contacts are actuated from the exterior of theenclosure by a solenoid type electromagnet. a

This invention has as a general object to improve the construction ofswitches of this character and to provide a stronger and simpler mannerof assembling the component parts of the 25 switch.

More specifically it is an object of this invention to provide a switchwhich is so constructed that alignment between the stationary andmovable contacts is assured automatically upon as- 30 sembly of thecomponent parts of the switch, and

which is self-insulating so that it may be mounted directly on a machinepart.

A further object of this invention is to provide a rigid and strongmounting means for the switch 85 structure and accompanying devices andto make the whole assembly universalfor mounting purposes in that noadditional insulation is necessary.

Still a further object of this invention is to provide a rigid anduniversal mounting means for 40 switches at a reduction in cost,material, weight,

and labor.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,com

45 bination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiment of the hereindisclosed invention may be 50 made as come within the scope of theclaims.

The accompanying drawings illustrate one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the 6 principlesthereof, and in which:

this application Janu FiEiSSUED Figure l is a front view of a switchembodying this invention, parts thereof being broken away and insection;

Figure 2 is a sectional view of the switch through Figure 3 on the planeof the line 2-2 showing particularly the arc enclosing chamber properlyassembled;

Figure 3 is a longitudinal sectional view through Figure 1 on the planeof the line 3-8.

Referring now particularly to the accompanying drawings in which likenumerals indicate like parts throughout the several views, the numeral 5designates a fiat sheet metal panel or backing plate upon which theswitch mechanism, indicated generally by the numeral 8, and itsactuating electromagnet I are mounted. The switch mechanism comprises aplurality of pairs of stationary contacts 8 adapted to be electricallybridged by movable contact units 9 actuated in a straight line motion bythe electromagnet.

The electromagnet I has a laminated field piece III which is rigidlymounted on the panel I by means of a bracket H. The field piece H) hassubstantially an inverted U-shape and has an armature i2 slidablyreceived between its legs, the lower ends of which are directed inwardlytoward each other to lie close to the armature.

Within the hollow of the field piece is a coil .il readily detachablyheld in place by channelshaped guideways ll in which the armatureslides.

The poles of the field piece are provided by downwardly extendingprojections I! on which shading coils I! are mounted in the customarymanner.

The armature I! is of inverted T-shape with its stem or shank slidablein the guideways l4 and its head projecting to opposite sides forcoaction with the poles l8. Like the field piece, the armature is oflaminated construction. A central lamination I8, is formed ofnon-magnetic metal and slidably projects through an opening is in thetop of the field piece.

Attached to the projecting upper end portion of the lamination I8 is acontact carrier 20. This carrier 20, which is fastened to the laminationl8 by a screw 2|, comprises a bar of molded insulating material with ametal insert 22 providing a reinforcing rib therefor. The front of themolded cross bar has a recess 23 to expose the adjacent central part ofthe metal reinforcing rib 22 so that the lamination i8 is engageabledirectly therewith.

The movable contact units (three in this instance) are mounted on t1carrier 20. The

formed jointly by the bottom walls 34 and 5i 0! the base and coversections, respectively, has

three holes 51 formed half in the base section and half in the coversection, as illustrated. These holes lead to the separated arcsuppressing compartments and are of a size to slidably receive thetelescoped spring enclosures 21 with just sumcient clearance for freesliding action. In other words, the telescoped spring enclosures 21substantially close the holes I! so that while the movable contacts areactuatable from without-the arc suppressing chamber, the completeness ofthe enclosure afforded thereby is not destroyed to the point ofinterfering-with the confinement of the are, but it is to be observedthat the clearance between the spring enclosures and the walls of theholes is sumcient to facilitate or enable rapid venting of accumulatedgases from within the chamber.

In operation, when the electromagnet is energized, the armature is'drawnup in a straight line to impart a straight line motion to the contactcarrier which lifts all of the movable contacts simultaneously fromtheir switch open positions to which they move by gravity into switchclosing positions with. each contact arm electrically bridging itsrespective pair of stationary contacts.

Upon 'deenergization of the electromagnet, the movable contact unitdrops to an open position thus simultaneously disengaging all of themovable contacts from their respective stationary contacts andbreakingreach line at two places. The are which tends to form uponopening of the switch is suppressed and quickly and effectuallyextinguished.

While it is not positively known just' what produces the exceptional arcextinction obtained with this switch, tests indicate that it must be thecombined effect of a number of structural features. Possibly the mostimportant element in the chainof causation is the close confinement ofthe arcs by the enclosure ofthe contacts within an insulating chamber ofrestricted volume resulting inter alia inthe development of highpressure within the chamber. This, together with the fact that the arcsare positively and forcibly projected in opposite directions away fromeach other and against opposite walls of the chamber by reason of therelative positions oi the stationary contacts and bridging bar and theconductors leading to the contacts, plus the deionizing effect which thesilver cadmium alloy of the contacts has upon the closely confined arcs,and the fact that the clearance between the spring enclosures and theholes through which the spring assemblies enter the chambercompartments, facilitates the escape or enables venting of theaccumulated gases from the interior or the chamber without delay afterextinction of the arc so that thechamber is cleared of any deleteriousand objetcionable gases to make it ready for a closely following cycle,possibly explains how this desirable arc quenching or suppressing effectis obtained. Stated briefly, it is thought to be the close confinementof the arc to produce a suppressing pressure, cooling of the arc bycontact with closely adjacent wall surfaces, the deionizing effect ofthe metal-of which the contacts are com posed and the rapid venting ofthe accumulated gases after' extinction of the are which bring thedesired results.

The cooling effect mentioned is augmented by shallow cavities 00 in thewalls which the arcs impinge.

From the foregoing description taken in connection with the accompanyingdrawings, it will be readily apparent to those skilled in the art, thatthis invention provides a substantial improvement in the constructionand design of plunger type electric switches and that by reason of thenovel are enclosing chamber flash-over between the poles of the switchis effectually prevented and as a consequence, instantaneous rupturingof the are is practically assured and the interruptingcapacity of theswitch is materially increased. i

It will also beapparent that the inherent design of the switch of thisinvention makes the same self-insulating so that it may be mounted onany non-insulating support. This very highly desirable feature is thedirect result of the particular construction oi the arc suppressingchamber in that all live parts of the switch are either carried directlyby or enclosed within this chamber which being, formed of a goodinsulating material provides all the insulation for the switch and thusentirely obviates the need for slate or other insulating panels.

What we claim as our invention is:

1. In an electric switch for industrial control service havingstationary and movable cohtacts tionary contacts are secured in fixedrelation to the plate but insulated therefrom, an electromagnet mountedon said plate and having an armature, and a driving connection betweenthe armature and the movable contact with a part thereof passing throughthe entrance opening.

2. In an electric switch, cooperating stationary and movable contacts, ametal back plate, a hollow structure of molded insulating materialenclosing the contacts and having the stationary contacts rigidlyattached thereto, means rigidly securing said hollow structure directlyto the back plate in frontwise removable relation, said securement ofthe hollow structure to the base plate securing the stationary contactsin definite relationship to the back plate while the contacts and an aredrawn therebetween upon opening of the switch are completely insulatedfrom the-back plate, an automatic actuating means rigidly mounted on theback plate so as to have fixed alignment with the contacts, and adriving connection between said automatic actuating means and themovable contacts passing through an opening in one wall oi the hollowstructure.

3. In an eiectricswitch, pairs of stationary contacts, a movable contactfor each pair of stationary contacts adapted to electrically bridge thesame, a metal bade plate adapted to be mounted in a vertical position,an insulating enclosure fixed to the base plate and enclosing thecontacts, said enclosure comprising a base section secured to the metalbase, a top section, and a front section, connections between thesections so formed that securement of the front section e subetontiellyvertical e,. and terminals to? ii male and the. stationary contentsbeing vaunted on the; top

the stationary contacts. said te section of the enclosure with theterminals on the exterior projecting upwardly away from the com

